On singular policies in the optimal distribution of a bifunctional catalyst: Part II. Effect of diffusional and mass transfer resistances


The effects of diffusional and mass transfer resistances on the optimal distribution of a bifunctional catalyst were studied for the case where each catalyst is supported on a separate carrier in the packed bed of a plug flow, tubular reactor. The width of the segment requiring a catalyst mixture is reduced by the presence of transport resistance due to shifts of both switching points away from the ends of the reactor. The extent of the change in each of the two switching point locations depends upon the relative magnitudes of the effectiveness factors for the two reactions, as does also the change of packing policy in the singular segment. As observed in Part I, the first switching location is again independent of the dimensionless residence time; in the presence of the transport resistance, however, the first switching location increases by the multiplier of the respective inverse effectiveness factors. The results from previous numerical studies were shown to be particular cases of these general analytic results, and one specific reaction scheme with first-order kinetics was studied in detail for illustration.